Foldable RFID device interposer and method

ABSTRACT

An RFID device interposer has folded ends that bring conductive lead end portions of conductive leads of the interposer to an underside of the interposer. The central conductive lead portions of the conductive leads remain on an upper surface of a dielectric substrate of the interposer. The folded ends of the interposer may be held together with an adhesive, or with thermal compression bonding. The interposer may also have an additional conductive material layer on an underside of the dielectric substrate. The conductive material layer may be capacitively coupled to the conductive leads of the interposer. The interposer may be tuned by varying the pressure used to secure the folded ends. This may be used to provide a better impedance match between a chip of the interposer, and the conductive leads and an antenna to which the interposer is coupled.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is in the field of radio frequency identification (RFID)devices, and methods for making such devices.

2. Description of the Related Art

Radio frequency identification (RFID) tags and labels have a combinationof antennas and analog and/or digital electronics, which may include forexample communications electronics, data memory, and control logic. RFIDtags and labels are widely used to associate an object with anidentification code. For example, RFID tags are used in conjunction withsecurity locks in cars, for access control to buildings, and fortracking inventory and parcels. Some examples of RFID tags and labelsappear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,692.

RFID tags and labels include active tags, which include a power source,and passive tags and labels, which do not. In the case of passive tags,in order to retrieve the information from the chip, a base station orreader sends an excitation signal to the RFID tag or label. Theexcitation signal energizes the tag or label, and the RFID circuitrytransmits the stored information back to the reader. The reader receivesand decodes the information from the RFID tag. In general, RFID tags canretain and transmit enough information to uniquely identify individuals,packages, inventory and the like. RFID tags and labels also can becharacterized as to those to which information is written only once(although the information may be read repeatedly), and those to whichinformation may be written during use. For example, RFID tags may storeenvironmental data (that may be detected by an associated sensor),logistical histories, state data, etc.

In many applications, it is desirable to reduce the size of theelectronics as small as possible. In order to interconnect very smallchips with antennas in RFID inlets, it is known to use a structurevariously called “straps,” “interposers,” and “carriers,” to facilitateinlay manufacture. Interposers include conductive leads or pads that areelectrically coupled to the contact pads of the chips for coupling tothe antennas. These pads provide a larger effective electrical contactarea than those of integrated circuits (ICs). The larger area reducesthe accuracy required for placement of ICs during manufacture whilestill providing effective electrical connection. IC placement andmounting are serious limitations for high-speed manufacture. The priorart discloses a variety of RFID strap or interposer structures,typically using a flexible substrate that carries the interposer'scontact pads or leads.

Improvements are desirable in many aspects of RFID devices in general,and in interposers for such devices.

SUMMARY OF THE INVENTION

According to an aspect of the invention, an interposer for an RFIDdevice has folded ends.

According to another aspect of the invention, an interposer for an RFIDdevice includes a conductive layer that is capacitively coupled toconductive leads of the interposer. The interposer may be tuned byvarying the thickness of a dielectric material between the conductiveleads and the conductive layer. The interposer may have folded ends thatfold around edges of the conductive layer.

According to yet another aspect of the invention, an RFID deviceinterposer is tunable by varying thickness of folded interposer ends.The thickness of the folded interposer ends may be varied by varying thepressure used to compress the folded ends, such as in a thermalcompression process.

According to still another aspect of the invention, an interposer for anRFID device includes: a dielectric substrate; and conductive leads on anupper surface of the dielectric substrate. Ends of the interposer arefolded to put substrate end portions and conductive lead end portionsunderneath a central substrate portion and conductive lead centralportions, with the conductive lead end portions facing downward.

According to a further aspect of the invention, a method of making aninterposer for an RFID device includes the steps of: forming conductiveleads on a top surface of a dielectric substrate; folding substrate endportions and conductive lead end portions underneath a central substrateportion; and securing the substrate end portions and the conductive leadportions in a folded configuration.

According to a still further aspect of the invention, an interposer foran RFID device includes: a dielectric substrate; and conductive leads onan upper surface of the dielectric substrate. Ends of the interposertransition from a substantially-planar first configuration in a centerof the interposer to a second configuration in which conductive lead endportions are offset from conductive lead central portions of theconductive leads.

To the accomplishment of the foregoing and related ends, the inventioncomprises the features hereinafter fully described and particularlypointed out in the claims. The following description and the annexeddrawings set forth in detail certain illustrative embodiments of theinvention. These embodiments are indicative, however, of but a few ofthe various ways in which the principles of the invention may beemployed. Other objects, advantages and novel features of the inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings, which are not necessarily to scale:

FIG. 1 is an oblique view of an RFID device interposer in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional view of the interposer of FIG. 1;

FIG. 3 is an oblique view illustrating a first step in the fabricationof the interposer of FIG. 1;

FIG. 4 is an oblique view illustrating a second step in the fabricationof the interposer of FIG. 1;

FIG. 5 is an oblique view illustrating a third step in the fabricationof the interposer of FIG. 1;

FIG. 6 is an oblique view illustrating a fourth step in the fabricationof the interposer of FIG. 1;

FIG. 7 is a plan view of an RFID device that incorporates the interposerof FIG. 1;

FIG. 8 is a cross-sectional view of the RFID device of FIG. 7;

FIG. 9 is an oblique view of an alternate embodiment RFID deviceinterposer in accordance with the present invention;

FIG. 10 is a cross-sectional view of the alternate embodiment interposerof FIG. 9;

FIG. 11 is an exploded side view of the alternate embodiment RFID deviceinterposer of FIG. 9;

FIG. 12 is a side view of another alternate embodiment of the RFIDdevice in accordance with the present invention, in a symmetricconfiguration;

FIG. 13 is a side view of the RFID device of FIG. 12, in an asymmetricconfiguration;

FIG. 14 is an oblique view of still another embodiment of the RFIDdevice in accordance with the present invention;

FIG. 15 is a bottom of the RFID device of FIG. 14; and

FIG. 16 is a bottom view of the RFID device of FIG. 14 coupled to acrossed dipole antenna.

DETAILED DESCRIPTION

An RFID device interposer has folded ends that bring conductive lead endportions of conductive leads of the interposer to an underside of theinterposer. The central conductive lead portions of the conductive leadsremain on a top side or upper surface of a dielectric substrate of theinterposer. The folded ends of the interposer may be held together withan adhesive, or with thermal compression bonding. The interposer mayalso have an additional conductive material layer on an underside of thedielectric substrate. The conductive material layer may be capacitivelycoupled to the conductive leads of the interposer. The folded ends ofthe dielectric substrate may be configured so as to completely cover theunderside of the conductive material layer after the folding isaccomplished. The interposer may be tuned by varying the pressure usedto secure the folded ends. Different pressures may be used to adjust thecapacitive coupling between the conductive layer and the conductiveleads. This may be used to provide a better impedance match between achip of the interposer, and the conductive leads and an antenna to whichthe interposer is coupled. The folded-end interposer provides aninexpensive way of coupling conductive leads across antennas withmultiple turns. In addition the interposer may be tunable as describedabove. A further advantage is that the interposer may have a moreuniform thickness, with the relative thickness of the folded endscompensating to a degree for the increased thickness in the middle ofthe interposer due to the presence of the chip.

FIGS. 1 and 2 show an interposer 10 with folded interposer ends 12 and14. The interposer 10 includes a dielectric substrate 16, and conductiveleads 18 and 20 on an upper surface 24 of the dielectric substrate 16. Achip 26 has contacts 28 and 29 that are electrically connected to theconductive leads 18 and 20. The chip 26 is an integrated circuit deviceused for communication with outside devices, by sending and/or receivingsignals via an antenna to which the interposer 10 is attached.

The interposer folded ends 12 and 14 include folded dielectric substrateend portions 30 and 32 and folded conductive lead end portions 34 and36. A central interposer portion 40 remains unfolded. The centralinterposer portion 40 includes a central dielectric substrate portion 42and conductive lead central portions 44 and 46. The interposer ends 12and 14 are folded over so as to put the substrate end portions 30 and 32and the conductive lead end portions 34 and 36 underneath the centralsubstrate portion 42 and the central conductive lead portions 44 and 46.

The interposer end portions 12 and 14 may be secured by attaching thesubstrate end portions 30 and 32 to the central substrate portion 42.This securement may be done with a suitable adhesive, such as a suitablepressure-sensitive adhesive. An adhesive layer 48 may be placed on alower surface 50 of the dielectric substrate 16. The adhesive layer 48may be placed by well-known coating or spraying operations. The adhesivelayer 48 may be a uniform layer, such as shown in the figures, oralternatively may be a patterned layer that covers only a portion of thelower substrate surface 50. As the interposer ends 12 and 14 are foldedthe portion of the adhesive layer 48 covering the substrate end portions30 comes into contact with the portion of the adhesive layer 48 coveringthe corresponding parts of the central substrate portion 42. Underpressure the two portions of the adhesive layer 48 bond together at eachof the interposer ends 12 and 14. This secures the interposer ends 12and 14.

As an alternative or in addition, the securement may be done withthermal compression bonding. Such thermal compression bonding involvesheating the substrate material at the interposer ends 12 and 14 whilethe ends 12 and 14 are under pressure. This causes reflowing of some ofthe substrate material at the interposer ends 12 and 14. Upon coolingthe substrate end portions 30 and 32 become firmly attached to thecentral substrate portion 42.

It will be appreciated that other suitable methods may be used to securethe folded interposer ends 12 and 14. An example of another alternativeis ultrasonic bonding.

The dielectric substrate 16 may be a polymer material, such aspoly(ethylene terephthalate) (PET). Alternatively, the dielectricsubstrate 16 may be a paper substrate. A wide variety of other suitablematerials may be used for the dielectric substrate 16. Examples ofsuitable materials for the RFID device substrate and the strap substrateinclude, but are not limited to, high glass-transition-temperaturepolycarbonate, poly(ethylene terephthalate) (PET), polyarylate,polysulfone, a norbornene copolymer, poly phenylsulfone, polyetherimide,polyethylenenaphthalate (PEN), polyethersulfone (PES), polycarbonate(PC), a phenolic resin, polyester, polyimide, polyetherester,polyetheramide, cellulose acetate, aliphatic polyurethanes,polyacrylonitrile, polytrifluoroethylenes, polyvinylidene fluorides,HDPEs, poly(methyl methacrylates), a cyclic or acyclic polyolefin, orpaper.

The conductive leads 18 and 20 may be aluminum or another suitable metaldeposited onto the substrate 16. Alternatively the conductive leads 18and 20 may be any of a wide variety of suitable conductive materials,such as conductive inks. Variety of suitable printing methods may beused for placing conductive inks in a suitable pattern for theconductive leads 18 and 20. Stamping and plating are other possiblemethods for putting the conductive leads 16 and 18 into place.

It will be appreciated that the conductive leads 18 and 20 may have anyof a wide variety of suitable shapes. Examples include rectangular andtriangular shapes.

The interposer ends 12 and 14 may be folded in any of a variety ofsuitable ways. One way that the folding can be accomplished is to movethe interposer 10 through a turning die, a die having shaped surfacesthat gradually turn the ends of the interposer 10 until the ends arefolded over. After the folding a pair of pinch rollers may be used topress the ends together. Such pressing may activate an adhesive toadhesively seal the interposer ends 12 and 14. The adhesive may beactivatable by other methods. Alternatively the pressing may be used inconjunction with heating to thermal compression bond the interposer ends12 and 14.

FIGS. 3-6 show steps in the production of the interposer 10. In FIG. 3the conductive leads 18 and 20 are placed on the dielectric substrate16. The conductive leads 18 and 20 are formed as described above on theupper surface 24 of the dielectric substrate 16. In FIG. 4 the chip 26is attached to the conductive layers 18 and 20. In doing so the contacts28 and 29 (FIG. 2) of the chip 26 are placed in contact with theconductive leads 18 and 20. In FIG. 5 the adhesive layer 48 is placed onthe lower surface 50 of the substrate 16.

FIG. 6 illustrates the turning of the interposer ends 12 and 14. Thisturning may be accomplished using a turning die, as described above.Finally, the interposer ends 12 and 14 are secured. This securement maybe done adhesively under pressure, such as from a pair of pinch rollers.Alternatively pressure and heating may be combined, as in the thermalcompression bonding described above. Other alternatives for thesecurement have also been described above. The result from the securingis the interposer 10 shown in FIG. 1.

The process illustrated in FIGS. 3-6 may be a roll-to-roll process or asheet process, for making multiple interposers 10 on a single sheet orweb of substrate material. The multiple interposers 10 may be singulatedby cutting or another suitable physical separation processes. Examplesof methods and devices for physical separation of interposers from websmay be found in commonly-owned U.S. Pat. No. 6,951,596, which isincorporated herein in its entirety.

It will be appreciated that some of the steps in the process describedabove may be performed in a different order than is described above. Forexample, placement of the chip 26 may be delayed until after formationof the folded interposer ends 12 and 14, if desired.

Turning now to FIGS. 7 and 8, the interposer 10 is shown as part of anRFID device 60. The RFID device 60 may be a tag or a label. The RFIDdevice 60 also includes a device substrate 64, and an antenna 66 formedon the device substrate 64. It will be appreciated that the RFID device60 may include many additional structures and/or features, for exampleprotective layers, printable layers, adhesive layers, and releaselayers. The antenna 66 is shown as a coil antenna having multiple turnsbetween antenna ends 68 and 70. The interposer 10 is attached to theantenna 66, with the conductive lead end portions 34 and 36 in contactwith or otherwise electrically coupled to the respective antenna ends 68and 70. The attachment of the interposer 10 to the rest of the RFIDdevice 60 may be accomplished by any of a variety of suitable methods,such as by welding, crimping, or use of adhesive. The conductive leadend portions 34 and 36 may be attached to the antenna ends 68 and 70using a conductive adhesive. However the attachment of the interposer 10to the rest of the RFID device 60 does not necessarily involve attachingthe conductive lead end portions 34 and 36 to the antenna ends 68 and70. One alternative is to have the middle portion of the adhesive layer48 (FIG. 1) adhesively attach the interposer 10 to the substrate 64 andan intermediate turn 72 of the antenna 66. Since no conductive materialis in contact with the intermediate turn 72, the interposer does notdirectly electrically couple to the intermediate turn 72 of the antenna66. The central substrate portion 42 prevents contact between theintermediate turn 72 and the central conductive lead portions 44 and 46.

The interposer 10 may be placed in contact with the antenna 66 by any ofa variety of machines or devices, including roll-to-roll processdevices, devices involving rollers, and pick-and-place devices. Examplesof roll-to-roll process may be found in U.S. Pat. No. 6,951,596 and U.S.Patent Application Publication No. 2007/0039687, both of which areincorporated herein in their entireties.

The folded interposer ends 12 and 14 may aid in providing a more uniformthickness for the installed interposer 10. As the interposer 10 engagesthe rest of the RFID device 60, the center part of the interposer 10 ispressed down into a space 80 between the lower parts of the foldedinterposer ends 12 and 14. The folded interposer ends 12 and 14 have athickness 84, which is greater than the thickness 88 of the substrate 16and the conductive leads 18 and 20 in the central interposer portion 40.This provides in essence thicker portions or “bumps,” at the interposerends 12 and 14. These thicker portions compensate to a degree for thethickness of the chip 26. By forcing the center interposer portion 40,along with the chip 26, into a space or well of sorts between theinterposer ends 12 and 14, the interposer 10 has a more uniformthickness, relative to interposers without folded ends.

To give one example, the chip 26 may have a thickness of 180 μm, withthe contacts 28 and 29 having a thickness of 18 μm. If the substrate hasa thickness of 50 μm, then if the substrate 16 does not have folded endsthere is a thickness difference of 198 μm between the center and sidesof the interposer. However, with the folded ends this thicknessdifference is reduced to 148 μm. Thus the thickness of the central“bump” of the interposer 10 may be reduced by 25% or more by use of thefolded ends 12 and 14.

FIGS. 9-11 show an alternate embodiment, an interposer 110 that has aconductive layer 184 attached to a lower surface 150 of the dielectricsubstrate 116. The interposer 110 has conductive leads 118 and 120 thatmay be similar to the conductive leads 18 and 20 of the RFID interposer10 (FIG. 1). The RFID interposer 110 also has a chip 126 that hascontacts 128 and 129 that are electrically coupled to the conductiveleads 118 and 120.

Substrate end portions 130 and 132 may substantially cover a bottomsurface 186 of the conductive layer 184, when the substrate end portions130 and 132 are wrapped around to form folded interposer ends 112 and114. Thus the substrate end portions 130 and 132 may extendsubstantially farther than conductive lead end portions 134 and 136. Theconductive lead end portions 134 and 136 may extend about the samedistance underneath as the folded conductive end portions 34 and 36 ofthe interposer 10 (FIG. 1). The extension of the substrate end portions130 and 132 to cover the bottom surface 186 may be done to prevent thematerial of the conductive layer 184 from being directly electricallycoupled to turns of a coil antenna, such as the intermediate turn 72 ofthe antenna 66 (FIG. 7).

Alternatively, the conductive layer 184 could be allowed to makeelectrical contact with one or more intermediate antenna turns 72.Connecting one or more of the intermediate turns 72 to the conductivelayer 184 could serve to capacitively couple part of the antenna 66 toboth of the chip contacts 128 and 129. This would provide an additionalcoupling between the antenna 66 and the contacts 128 and 129, whichwould also still be directly electrically coupled to other parts of theantenna 66, such as ends of the antenna 66. This could potentiallycreate multiple differently tuned responses.

Another possible reason for making electrical contact between theconductive layer 184 and one or more intermediate turns 72 is to shortout some of the coils of a coil antenna to effectively tune the antenna.Using this mechanism, the tuning of the antenna 66 may be controllableby controlling a gap between the end portions 130 and 132. It will beappreciated that the principles described do not apply only to coilantennas, but may also apply to other types of antennas, such as UHFantennas.

A top surface 188 of the conductive layer 184 may be adhesively orotherwise attached to the bottom surface 150 of the dielectric substrate116. The conductive layer 184 may be made of a suitable deposited metal,metal foil, or other electrically conductive material. Example materialsinclude copper, silver ink, and aluminum. The conductive layer 184should be of adequate conductivity such that the loss of RF energycoupled through the layer 184 is small relative to other energy lossesin the device. Any of a variety of suitable thicknesses may be used, forexample (without limitation) thicknesses from 500 nm to 18 μm. Theconductive layer 184 may be made of the same material as the conductiveleads 118 and 120.

In operation the conductive layer 184 is capacitively coupled to theconductive leads 118 and 120. This affects the electricalcharacteristics of the RFID interposer 110. It will be appreciated thatthe capacitive characteristics of the electrical coupling between theconductive layer 184 and the conductive leads 118 and 120 depend uponthe thickness of the dielectric material between the conductive layer184 and the conductive leads 118 and 120. By controlling the thicknessof the intervening dielectric material, the electrical characteristicsof the RFID device 110 may be controlled or tuned to some extent. Inmany methods for forming the folded interposer ends 112 and 114,pressure is used to squeeze portions of the dielectric layer 116. Thethickness of the dielectric layer 116 may be permanently altered by theapplication of pressure, especially in securement methods that involveheating and reflowing of material of the dielectric layer 116. Usingsuch methods, the securing the folded interposer ends 112 and 114 mayalso be used for tuning the electrical characteristics of the RFIDinterposer 110. Controlled amounts of pressure in one or more sets ofrollers may be used to set the thickness of the dielectric material 116between the conductive layer 184 and the conductive leads 118 and 120.Different pressures may be used to tune the RFID interposer 110 fordifferent types of antennas, and/or for different types of chips.Alternatively or in addition, the pressure used in securement of theinterposer ends 112 and 114 may be used to tune individual RFIDinterposers based on individual characteristics of each interposer. Itwill be appreciated that the pressure, perhaps in conjunction withheating, may be used after the ends 112 and 114 have been initiallyfolded over and secured. That is, pressure may be applied to altercapacitive characteristics independent of an operation to secure thefolded interposer ends 112 and 114.

FIGS. 12 and 13 illustrate another embodiment, an interposer 210 thathas long conductive leads 218 and 220 that may be folded so as to haveto produce themselves a conductive layer 290 on an underside 294 of afolded dielectric substrate 296. The folded substrate 296 consists offolded layers of a substrate 216 upon which the conductive leads 218 and220 are attached. The conductive layer 290 is made up of foldedconductive lead end portions 234 and 236. The conductive lead endportions 234 and 236 extend across most of the lower surface of thefolded dielectric substrate 216, but do not make contact with oneanother. The folded conductive lead end portions 234 and 236 cover mostof the underside of the substrate 216, and thus overlap most ofconductive lead central portions 244 and 246. The folded end portions234 and 236 may thus function in a manner similar to that of theconductive layer 184. That is, the conductive lead end portions 234 and236 may be capacitively coupled to the conductive lead central portions244 and 246 that provide a parallel overlap with the end portions 234and 236. This capacitive coupling may influence electricalcharacteristics of the interposer 210.

It will be appreciated that the electrical characteristics of theinterposer 210 may be controlled by controlling the way that interposerends 212 and 214 are folded. FIG. 12 shows a symmetric folding, with achip 226 located over the middle of the folded substrate 296. In thesymmetric configuration in FIG. 12 the folded conductive lead endportions 234 and 236 are symmetrically underneath the conductive leadcentral portions 244 and 246. Chip contacts 228 and 229 overlierespective folded conductive lead end portions 234 and 236.

FIG. 13 shows an asymmetric folding configuration of the interposer 210.The asymmetric folding configuration 210 may be the same as thesymmetric configuration shown in FIG. 12, except for the difference inthe folding. In the illustrated asymmetric configuration the conductivelead end portion 234 is longer than the conductive lead end portion 236.The conductive lead central portion 246 is longer than the conductivelead central portion 244 by a corresponding amount. The chip 226 islocated to one side of the folded substrate 296. The chip contacts 228and 229 are in contact with the conductive lead central portions 244 and246, respectively. As is shown in FIG. 13, both of the chip contacts 228and 229 may overlie the conductive lead end portion 234. Altering theposition of the folding of the interposer 210 from the symmetricconfiguration shown in FIG. 12 changes the electrical coupling betweenthe various parts of the interposer 210. This changes the electricalcharacteristics of the interposer 210, effectively tuning the interposer210 merely by changing the fold locations. It will be appreciated thatchanging the fold locations for the interposer 210 may be accomplishedby altering the position in which the interposer 210 enters a turningdie or other folding device.

It will be further appreciated that a wide variety of alternatives arepossible for the configuration of the interposer 210. The interposerends may overlap each other in part, to give one example. Longer ends ofthe substrate 216 may be used to cover parts of either of the conductivelead end portions 234 and 236.

FIGS. 14 and 15 show another alternate embodiment, an interposer 310that has folded ends 312 and 314. The interposer 310 has four conductiveleads 318, 319, 320, and 321 on a substrate 316. The conductive leads318-321 produce four respective folded conductive lead end portions 334,335, 336, and 337 when the ends 312 and 314 are folded over. Theconductive leads 318 and 320 are coupled to signal contacts of a chip326. The conductive leads 319 and 321 are coupled to ground contacts ofthe chip 326. This configuration, with two signal contacts in line onone side of the chip 326, and two ground leads in line on the other sideof the chip 326, is a common configuration for RFID chips.

Referring now in addition to FIG. 16, the interposer 310 is showncoupled to a crossed dipole antenna 366. The crossed dipole antenna 366includes a pair of signal arms 368 and 370 in a single line. The crosseddipole antenna 366 (an example of a broad category of couplingstructures) also includes a pair of ground arms 372 and 374 in a line,and substantially perpendicular to the signal arms 368 and 370. Theground arms 372 and 374 are electrically coupled together by a shortperpendicular crosspiece of conductive material 378. The interposer 310engages the crossed dipole antenna by having the signal conductive leadend portions 334 and 336 in contact with the signal arms 368 and 370.The ground conductive lead end portions 335 and 337 are in contact withrespective ends of the crosspiece 378 of the crossed dipole antenna 366.This places both of the ground contacts of the chip 328 in electricalconnection with the ground arms 372 and 374 of the crossed dipoleantenna 366. The interposer 310 thus provides a way of coupling a commonfour-contact chip, with side-by-side signal contacts and side-by-sideground contacts, with a crossed dipole antenna configuration in whichsignal arms and ground arms alternate.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described elements (components, assemblies,devices, compositions, etc.), the terms (including a reference to a“means”) used to describe such elements are intended to correspond,unless otherwise indicated, to any element which performs the specifiedfunction of the described element (i.e., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function in the herein illustratedexemplary embodiment or embodiments of the invention. In addition, whilea particular feature of the invention may have been described above withrespect to only one or more of several illustrated embodiments, suchfeature may be combined with one or more other features of the otherembodiments, as may be desired and advantageous for any given orparticular application.

1. An interposer for an RFID device, the interposer comprising: adielectric substrate; and conductive leads on an upper surface of thedielectric substrate; wherein ends of the interposer are folded to putsubstrate end portions and conductive lead end portions underneath acentral substrate portion and conductive lead central portions, with theconductive lead end portions facing downward.
 2. The interposer of claim1, wherein the substrate is a polymer substrate.
 3. The interposer ofclaim 1, wherein the substrate is a paper substrate.
 4. The interposerof claim 1, further comprising a chip attached to the central conductivelead portions on the top side of the substrate.
 5. The interposer ofclaim 1, wherein the substrate end portions are in contact with andattached to a lower surface of the central substrate portion.
 6. Theinterposer of claim 5, wherein the substrate end portions are thermalcompression bonded to the central substrate portion.
 7. The interposerof claim 5, wherein the substrate end portions are adhesively attachedto the central substrate portion.
 8. The interposer of claim 1, furthercomprising a conductive layer; wherein an upper surface of theconductive layer is attached to a lower surface of the substrate.
 9. Theinterposer of claim 8, wherein the conductive layer is capacitivelycoupled to the conductive leads.
 10. The interposer of claim 9, whereinthe substrate end portions are thermal compression bonded to theconductive layer.
 11. The interposer of claim 10, wherein strength ofthe capacitive coupling between the conductive layer and the conductiveleads varies as a function of pressure used in the thermal compressionbonding; and wherein the interposer is a tunable interposer tunable byselecting the pressure used in the thermal compression bonding.
 12. Theinterposer of claim 8, wherein the substrate end portions coversubstantially all of a lower surface of the conductive layer.
 13. Theinterposer of claim 1, wherein the conductive lead end portions overlapmost of the conductive lead central portions.
 14. The interposer ofclaim 13, further comprising a chip attached to the central conductivelead portions on the top side of the substrate.
 15. The interposer ofclaim 14, wherein the chip is symmetrically located relative to theconductive lead end portions.
 16. The interposer of claim 14, whereinthe chip is asymmetrically located relative to the conductive lead endportions.
 17. The interposer of claim 1, wherein the conductive leads tonot extend to a center of a lower surface of the interposer.
 18. Theinterposer of claim 17, as part of an RFID device; wherein theconductive lead end portions are coupled to a coupling structure of theRFID device; and wherein conductive material of the coupling structureis in contact with the center of the lower surface of the interposer.19. The interposer of claim 1, wherein the conductive leads include atleast four conductive leads.
 20. An interposer for an RFID device, theinterposer comprising: a dielectric substrate; and conductive leads onan upper surface of the dielectric substrate; wherein ends of theinterposer transition from a substantially-planar first configuration ina center of the interposer to a second configuration in which conductivelead end portions are offset from conductive lead central portions ofthe conductive leads.
 21. The interposer of claim 20, wherein theconductive lead end portions are offset from the conductive lead centralportions in a direction substantially perpendicular to a plane of thesubstantially-planar first configuration.
 22. The interposer of claim21, wherein the ends are folded ends.